1. Field of the Invention
The present invention relates to a multicylinder rotary compressor, and more specifically it relates to a multicylinder rotary compressor, which is adapted to operate a plurality of rotary compressing elements during high rotation speed and to operate only one rotary compressing element during low rotation speed, and a compressing system and a refrigerating unit provided with the multicylinder rotary compressor respectively.
2. Description of the Related Art
A rotary compressor, which is a compressor for compressing a refrigerant gas used in an air-conditioner, a refrigerator or the like and has a structure in which two rotary compressing elements are disposed at upper and lower portions, has been known. There is a rotary compressor, which simultaneously compresses the refrigerant gas with two rotary compressing elements, discharges the compressed refrigerant gas into a closed vessel and takes out the compressed refrigerant gas through a discharge pipe provided in the closed vessel. The rotary compressor is referred to as a two-cylinder rotary compressor hereinbelow. Further, there is another rotary compressor in which a motor-operating element provided in a closed vessel is an inverter type and the number of revolutions of a rotating shaft, which rotates through a rotor of the motor-operating element can be varied in accordance with the output. This compressor is disclosed in for example Japanese Patent Laid-Open Publication No. 07-229495.
The above-mentioned conventional two-cylinder rotary compressor will be described schematically. For example, as shown in FIG. 3, the two-cylinder rotary compressor comprises a motor-operating element B and a rotary compressing element C in a closed vessel A so that the motor-operating element B and the rotary compressing element C are positioned at upper and lower portions respectively. The rotary compressing element C includes a first rotary compressing element C1 and a second rotary compressing element C2. A vane E1 abuts on a roller D1, which eccentrically rotates in a compressing chamber in the first rotary compressing element C1 with the vane E1 biased by a spring F1, resulting in that the vane E1 defines between a low pressure chamber and a high pressure chamber in the compressing chamber. Similarly, a vane E2 abuts on a roller D2, which eccentrically rotates in a compressing element C2 with the vane E2 biased by a spring F2, resulting in that the vane E2 defines between a low pressure chamber and a high pressure chamber. The refrigerant gas compressed in the compressing chamber in the first rotary compressing element C1 and the refrigerant gas compressed in the compressing chamber in the second rotary compressing element C2 are discharged into the closed vessel A.
In the above-mentioned two cylinder rotary compressor, a through hole G1 is provided in the first rotary compressing element C1, through which a part of high-pressure refrigerant gas discharged into the closed vessel A is passed to apply back pressure to the vane E1. Thus, by the addition of the backpressure to a biasing force of the spring F1, the vane E1 is adapted to be in intimate contact with the roller D1. Also, a through hole G2 is provided in the second rotary compressing element C2, through which a part of high-pressure refrigerant gas discharged into the closed vessel A is passed to apply back pressure to the vane E2. Thus, by the addition of the backpressure to a biasing force of the spring F2, the vane E2 is adapted to be in intimate contact with the roller D2.
Further, a compressing system provided with a conventional multicylinder rotary compressor is comprised of a multicylinder rotary compressor, a control device, which controls an operation of the multicylinder rotary compressor, and the like. And when a driving element is driven by the control device, a low pressure gas is sucked into the respective low pressure chamber sides of the cylinders in the first rotary compressing element and the second rotary compressing element from a suction passage and is respectively compressed by the operations of each roller and each vane to be high pressure refrigerant gas. Then the high pressure refrigerant gas is discharged from the high pressure chamber sides of the respective cylinders to a discharge muffling chamber through a discharge port and then is discharged into the closed vessel A and is then discharged outside. The structure of the compressing system provided with the conventional multicylinder rotary compressor is disclosed in Japanese Patent Laid-Open Publication No. 05-99172, for example.
In the above-mentioned conventional two cylinder rotary compressor, since the motor-operating element B is an inverter type and the number of revolutions of the rotating shaft H is controlled, an operation over a wide range between the a low rotation speed and a high rotation speed can be made. However, when designing is generally carried out so that properties in a wide operation range can be ensured, the COP (coefficient of performance) during operation, which requires a low refrigerating capacity, is lowered by downs of the motor efficiency and pump efficiency during a low rotation speed.